Not blowing hot air inside the cabin

The air blowing inside the cabin of my A4 is not hot, it does blow some hot air but not enough to warm someone. The engine temp reaches almost half of the mark ( needle is one line before the middle) and the temperature stays there all the time. Turn the fan inside to start blowing hot air and nothing changes much as I am increasing the temp, 75, 80, 81 and finally hi.... it does blow air but not hot enough.
I have checked the coolant to be sure is full and that is the case. I am not sure what else to look, I do not know if the 2000 A4 comes with a bypass valve to allow hot liquid to pass by the cabin recirculator...

Hello edupin: Had the same issue with my '97 A4 2.8Q. Arizona car, brought to Minnesota. Prior owner apparently never flushed system. I flushed and refilled entire system, but took an extra step, disconnecting the heater hoses at the fire wall and using compressed air to BLOW out the gunk that didn't loosen up with a normal flush. This did the trick. Hopefully, one ever mixed regular green coolant with your orange G12. This combination will almost always result in a bad prognosis for a cooling system. Good luck. audiphile1

Quote:

Originally Posted by edupin

The air blowing inside the cabin of my A4 is not hot, it does blow some hot air but not enough to warm someone. The engine temp reaches almost half of the mark ( needle is one line before the middle) and the temperature stays there all the time. Turn the fan inside to start blowing hot air and nothing changes much as I am increasing the temp, 75, 80, 81 and finally hi.... it does blow air but not hot enough.
I have checked the coolant to be sure is full and that is the case. I am not sure what else to look, I do not know if the 2000 A4 comes with a bypass valve to allow hot liquid to pass by the cabin recirculator...

Thank you very much for the input. I will see if I can get this done over this long weekend.... having to drive with big gloves in this Colorado weather is getting old... specially in the cold mornings.

check the vacuum line comming from the heater core. this was my problem. it was all cracked and split underneath the black engine cover so you couldnt hear it untill you took the cover off. sure enough, did that and fixed the heat issue no problem. goodluck! i went two winters in my b5 without heat.

the vacuum "line" is comming right out of the heater core you really cant miss it. theres two big hoses (prabably 21/2 or 3 inch) those are your coolant hoses. then theres a really small vacuum line coming right where the hoses are commin from. like i said you really cant miss it.

The heater core is actually inside your car, but it's behind all the dash stuff. It's a real PITA to replace. The coolant flush for the heater core is a good idea, however, you'll likely need to replace it at some point, just not now hopefully.

To flush the heater core:

1. The coolant hoses that are attached to the heater core are located under the hood. There is a plastic cover up by the fire wall (by windshield) that cover the batter and some other things. Remove this plastic cover and you'll see the battery with two coolant hoses next to it (closer to the driver side). These two hoses move coolant into and out of the heater core, which allows your cabin to receive warm air when the heater is on.

2. Disconnect both hoses and be prepared for a little coolant to leak out. To try and prevent this, drain some of your coolant. You can do this by removing the plastic grill at your driver side fog light. After you pull that off you'll see a red plastic piece. Use a flathead or a large phillips screwdriver to turn this red piece and you'll see coolant flow out. Close that valve after draining some of the coolant. Remember to put only the recommended (likely G12) coolant back in.

3. At this point, you a have a couple of options. Here's what I did which I think works best compared to everything else I've heard for flushes these heater cores. Go to a hardware store (like home depot) and by some tubing that will fit over the heater core connections. You can find the same size as the coolant pipe. Just measure the interior diameter of the coolant pipe before going to the store to make sure you get the right side. I would purchase about 8 feet of it. When you get home, cut that hose in two, with one piece being 3 ft and the other being 5 feet. The longer piece you can connect to either side of the heater core and let it hang over the car with something something ready to cash the flushing fluid (use an oil catcher or something). Be sure to put towels around that area to prevent splattering and also you'll want to cover your car so coolant doesn't get onto the paint. For the 3 foot hose, attach it to the other side of the heater core and than attach a funnel to the other end. This funnel is where you'll pour a cleaning solution that will flush your core.

4. For a cleaning solution, there are a lot of options. I found that OxyClean works the best. Also, use extremely hot water. Mix about 1/2 to 1 gallon and then pour into funnel, holding the funnel up in the air so gravity can do the work. Eventually, you'll begin see/hear fluid coming out the end of the other hose. After you complete this, switch the hoses at the heater core and do it all over again, going in the other direction.

5. When completed, I used an air compressor to blow-out the remaining gunk, which proved to be VERY advantageous, as a lot of gunk came out. Then, the last step to is flush again with only warm water to remove chemicals and any other lose gunk. Reattach factory hose, add coolant and start the engine. Let it run for about 10 minutes or until car temp is warm, turn on heater and hope for the best!

Hey todd: Excellent overview. We must have simiiar DNA, as what you did is almost identical to what I used to cure my heat problem (although I raised the temporary hose ends and filled the entire core with Prestone Super Radiator Cleaner and let it sit overnight). I agree that using the compressed air gets results that are absolutely critical in getting the gunk out of the core. vwdawg/audiphile1

Oh...forgot to mention to edupin...when you are finished with everything, don't forget to disconnect and elevate the coolant reservoir four or five inches. One of the heater hoses has a very small hole in it. You must loosen the clamp and pull that hose back an inch or so until coolant spurts out of that small hole, then push it back on and retighten. If you don't do this bleed procedure, air will remain in the core and you won't get the heat you are looking for. vwdawg/audiphile1

I've been searching for two days on how to bleed the heater core. I keep hearing about some hole in one of the hoses that go to the core, and that you have to slightly take one of the hoses off to expose this hole. Help me out here. I must be blind....

-Can someone show a picture of this hole?
-Which tube is it on, the left (out) or right (in)?
-Is the hole on the top, bottom, left, or right of the hose?

I just flushed the core and still don't have heat. I'll flush the whole system as soon as I figure out why I'm not getting heat. Someone please show me or describe better this bleed hole. It is friggin cold!!!